US President Donald Trump opened up a new controversy as he defended American gun laws by contrasting them with London’s stringent anti-gun legislation, claiming it resulted in one of the British capital's hospitals turning into a “war zone” due to a rise in knife crime instead.

In a speech to the National Rifle Association (NRA) in Dallas, Texas, yesterday in which he spoke out in favour of liberal gun laws, the US president sarcastically questioned whether vans, trucks and cars, which have been used as weapons by terrorists, should also be banned before turning to knives.

“I recently read a story that in London, which has unbelievably tough gun laws, a once very prestigious hospital, right in the middle, is like a war zone for horrible stabbing wounds,” Trump said.

“Yes, that’s right, they don’t have guns, they have knives and instead there’s blood all over the floors of this hospital. They say it’s as bad as a military war zone hospital,” he added.

He then went on to make a stabbing gesture in the air several times and muttered, “Knives, knives, knives".

Trump is due to visit the UK on July 13, after previously cancelling a trip amid calls for mass protests on the streets of Britain. His latest comments also triggered a strong reaction, with London trauma surgeon Dr Martin Griffiths offering to give Trump a tour of his “prestigious” Royal London Hospital. It is believed Trump was referencing a comment made by Dr Griffiths during a BBC Radio interview earlier this year.

“Happy to invite Mr Trump to my (prestigious) hospital to meet with our mayor and police commissioner to discuss our successes in violence reduction in London,” Griffiths tweeted, alongside an image which indicated the US president had missed the point of his statement.

At least 38 people in London have lost their lives to knife crime so far this year as the city saw a spike in stabbings, according to Scotland Yard.

Marian Fitzgerald, a criminologist at the University of Kent, said although there had been a spike in knife-related deaths in London, it was a separate issue to gun control.

"It's just politically convenient, in a speech to the gun rights lobby, to try and make those comparisons and they are totally spurious. If he needs reassurance, Donald Trump is going to be much safer in London than he would be at home," she said.

This is not the first time Trump has made a controversial statement related to the British capital’s safety record.

Last year, Trump criticised London Mayor Sadiq Khan, hours after a deadly terrorist attack, based on a misinterpretation of an outdated tweet. Khan’s office had said at the time that the mayor had “more important things to do than respond to Donald Trump’s ill-informed tweet that deliberately takes out of context his remarks”.

“If he comes to London, President Trump will experience an open and diverse city that has always chosen unity over division and hope over fear. He will also no doubt see that Londoners hold their liberal values of freedom of speech very dear,” the London ayor said in a tweet last month when Trump’s July visit was confirmed.